This invention relates to the manual assessment of muscle strength. More particularly, the invention relates to a portable, manual muscle tester and to the method of using same.
Manual muscle testing is the most widely used method of physical examination for clinical evaluation of muscle strength. Manual tests are commonly used to monitor a patient's progress during an extended period of rehabilitation or recovery. These tests are also used to determine differences in strength between individuals and to determine strength deficits in a given individual. In the latter case, deficits are detected by the comparison of contralateral limb segments or muscle groups. Manual muscle tests are employed, as well, to locate weakness in areas not previously suspected by the patient. The area of weakness is often far removed from the site of pathology, and such weaknesses are related to the musclo-skeletal linkage systems of the body. Manual testing is also used in the design of rehabilitation or strengthening programs for individuals who have been injured or wish to undertake an activity for which they are not properly conditioned.
Typically an examiner (and by this is meant a physician, therapist, athletic trainer, or coach, for example) asks a patient to maintain a specific posture with the limb being tested. The examiner applies pressure downward with one or two hands and judges subjectively the patient's resistance. For example, the examiner may judge the force he must apply to a limb in order to lower it from a raised position. The resistance is quantified subjectively with a grade from 5 (maximal) to 0 (no contraction). For purposes of comparison, a patient's unaffected limb is similarly tested. From day to day or week to week, the examiner relies on a subjective determination to measure the patient's progress.
Manual muscle testing is essentially a subjective evaluation and is unreliable when performed by different individuals who may use different techniques. Several attempts to standardize manual testing procedures have been made and many devices to measure strength have been proposed. One of the earliest, which dates back to 1912, is a spring scale device. Lengthy reviews are now available on various devices and their use. Despite the obvious disadvantages of a subjective test of a muscle strength, manual muscle testing, without instrumentation, continues to be the predominant method used in the clinical setting. Until recently, few, if any, dynamometers (strength measuring devices) offered objective, accurate evaluation of dynamic muscle strength.
The patent literature proposes devices for measuring strength. For the most part, these are large, cumbersome, immobile, and specially adapted to test particular muscles, those of the legs, for example, or those of the arms. In one case, portability of a test device is recognized and a fluid filled cylinder and pressure gage arrangement is suggested. No provision is made for this device to retain the maximum pressure gage reading. A dial gage indicates force applied to the fluid cylinder plunger and typically these are much harder to read than a clear digital, numeric force indication, particularly when the indication quickly varies, as in all muscle testing procedures.
The physician, physical therapist, athletic trainer who tests a subject's strength is aware of what muscles contribute what forces and in what directions. A simple example clarifies the importance of selective measurement. A subject's leg is commonly tested by having the subject sit and raise his foot off the floor. The examiner applies pressure downward at the knee gradually until he overcomes the subject's resistance and the leg moves downward. The examiner is interested in those muscles resisting downward force. In this test, the examiner is not concerned, for example, with the forces resisting rotational movement from the hip to the knee, or those forces resisting movement of the leg from side to side. Likewise, the examiner does not want his measurement to include force components directed longitudinally along the upper leg to the hip. A manual muscle tester should permit the examiner to distinguish between the forces that are of interest, and those that are not.
For ease of operation, a portable manual muscle tester should be simply used, preferably in a manner closely akin to the testing that the examiner currently uses. The unit should be easy to operate without elaborate attachment to the patient or subject, should be easy to read, afford repeatability in its strength indications from one test to the next, should require no elaborate or time consuming setup procedure, and should be of a size, shape, and weight such that the examiner will readily keep it with him throughout the day.